Dead-weight Testers Research Articles

GET 43-2022 State Primary Standard for the unit of excess pressure within the static pressure range of 10–1600 MPa and the pulse pressure range of 1–1200 MPa and the effective area of piston-cylinder assemblies in deadweight testers within the range of 0.05–1 cm2

GET 43-2022 State Primary Standard for the unit of excess pressure within the static pressure range of 10–1600 MPa and the pulse pressure range of 1–1200 MPa and the effective area of piston-cylinder assemblies in deadweight testers within the range of 0.05–1 cm2

The Measurement Method of a Piston Fall Rate

The accurate determination of the piston fall rate is one of critical parameters in dead weight testers and piston gauges, as it confirms a quality of machining, instrument accuracy class, and long-term stability. This study introduces a method for determining piston fall rate using two triangulating laser distance sensors. This approach offers versatile applicability, in high-precision standards as well as in regular-class instruments, and is robust in accommodating variations in measurement ranges, pressure transmitting mediums, materials of weights, and weight diameters. The method utilizes two laser sensors symmetrically positioned under the primary weight of the piston pressure gauge, allowing for seamless measurements without the need for sensor adjustments. The data collected from these sensors are processed to calculate the average displacement of the primary weight. The method’s effectiveness is demonstrated with high linearity and precision in determining the piston weight fall rate. This approach can lead to improvements in fluid dynamics analysis and metrology of precise pressure balances. The method’s advantages include error mitigation and reduced operator intervention, making it highly suitable for applications requiring accurate piston descent velocity measurements, particularly in older measuring instruments. The establishment of a reference dataset can enhance the accuracy of periodic examinations of piston-cylinder assemblies, thereby reducing costs and improving measurement quality.

Development of alumina-based porosity reference materials for the mercury porosimetry method

This paper presents the results of a study on the development of alumina-based porosity reference materials (RMs), which are intended for controlling the accuracy of the measurement results obtained using the mercury porosimetry method. These mercury porosimetry RMs are being developed in the Russian Federation for the first time and are primarily intended for verification / calibration and testing for type approval of mercury porosimeters. The study of metrological characteristics was conducted using a reference system, which is to be included in the GET 210-2014 State Primary Measurement Standard for units of specific gas adsorption, specific surface area, specific volume and pore size of solid substances and materials. This reference system was calibrated prior to conducting the study with the use of external reference pressure sensors of the 2nd order at 0.6 MPa and 400 MPa, as well as a laboratory balance (special accuracy class 1) having a maximum weighing limit of220 g. In the course of conducted research work, procedures for reproducing and estimating the uncertainty of porosity characteristics using the mercury porosimetry method were developed. When estimating the PM metrological characteristics, the standard uncertainty, associated with the characterisation and heterogeneity of the studied materials (PM candidates), was evaluated. The standard uncertainty due to instability was disregarded due to the high stability of the alumina matrix. According to the results of the conducted studies, four types of alumina-based porosity PM were developed. Their pore sizes are of about -lOnm; -2,000 nm; -9,000 nm; -60,000 nm. The RMs with pore sizes of -10 nm; -2,000 nm were intended for use in controlling the accuracy of mercury porosimeters operating at high pressures, while the RMs with pore sizes of -9,000 nm; -60,000 nm were for controlling the accuracy of mercury porosimeters operating at low pressures. The developed RMs are different from their foreign counterparts, which are produced by BAM (Germany) and NIST (USA) metrological institutes. The standard uncertainty due to characterisation of the RMs in question was estimated, not by the method of interlaboratory experiment, but by a full analysis of the constraint equations taking into account all sources of uncertainty included in the equations on the basis of the Guide to the Expression of Uncertainty in Measurement. The conducted studies allowed the RM certified values to be traceable at this stage to the GET 3-2008 State Primary Measurement Standard for the mass unit (kilogram), the GET 101-2011 State Primary Measurement Standard for the pressure unit in the field of absolute pressure in the range 1×10 –1 – 7×10 5 Pa, the GET 43-2013 State Primary Measurement Standard for the pressure unit in the range 10-1600 MPa and the effective area of the piston-cylinder unit of dead weight testers in the range 0.05-1 cm 2. In addition, a reference material having a large pore size of -60,000 nm, which currently has no analogues elsewhere in the world, was characterised.

An Examination of the Uncertainty of Industrial Deadweight Testers Used for Pressure Calibrations in Different Environments

The industrial deadweight tester (IDWT) is a dead weight pressure gauge that is designed, built, and calibrated to be used without having to make corrections or calculate pressure. In practice, the...

Evaluating performance of a fuel nozzle test stand under varying configurations using Taguchi parameter design - An industrial application

Taguchi parameter design is an efficient and effective method for evaluating and optimizing parameters for a given process. This article describes a study involving the use of Taguchi parameter design for the evaluation of pressure measurement devices used on fuel nozzle test stands. This study examines and compares the performance of a digital display pressure transducer device and a mechanical analog pressure gage, under various parameter levels and configurations. Both an inner and outer orthogonal array are used to quantify control factor variability within the pressure gage calibration and measurement process, given two noise factors. Control factors include two types of dead weight testers, two types of pressure measurement devices, and three set pressures. Two noise factors utilized here were two different operators and the change in direction of the pressure before measurement (upward or downward). Collected data are used to determine the optimal levels of three quality characteristics: pressure difference, settling time, and hysteresis. Taguchi parameter design analysis of signal-to-noise ratio (S/N ratio) found an optimal test stand configuration included a pressure transducer with digital display with any combination of the other control factors, although with some sacrifice of response time. Verification of this selected configuration was conducted through linearity studies.

Liquid and gas in dead-weight pressure-gauge testers

It is demonstrated that the density and viscosity of liquids and gases exert different effects on the effective area of piston-cylinder assemblies even at comparatively low pressures, as a consequence of which a change in the working medium in the piston-cylinder assemblies of high-precision dead-weight pressure-gauge standards may be accompanied by a marked change in the reproducible pressure. The feasibility of creating a system for assuring the correctness of pressure measurements in gas media, including a state standard, is evaluated.

Revised characterization of the controlled clearance piston gauge

A revised equation is presented for the effective piston area of controlled clearance deadweight testers from the theory of elasticity which accounts for the semi-infinite loading of the measured pressure cylinder. The concept of pressure transmissibility expressed in terms of transmission delay threshold pressure and the importance in the choice of operating fluids is discussed. Test results illustrating pressure transmissibility for 25 different fluids at pressure between 138 MPa (20 000 psi) and 1380 MPa (200 000 psi) are presented, together with proposed ranking of the fluids based on their relative pressure transmissibility. The linear nature of the stall curve with fluids of high transmissibility and the resulting linear nature of the adjustments to the effective area are shown. The linearity allows the use of considerable extrapolation for making reasonable estimates of effective area, where direct knowledge of the slope of the stall curve is not known. The robustness of the new equation is demonstrated by applying the equation to data from two mercury point experiments at Harwood (9 years apart), several National Institute of Standards and Technology (NIST) characterizations of controlled clearance gauges, some other experiments at Harwood, and the data from NIST’s experiment using a controlled clearance piston gauge to isolate the transition pressure of bismuth from Bi I to Bi II. The conclusions reached indicate that with suitable operating fluids, there is a negligibly small difference between pressure values calculated from the method discussed here and that used by NIST based on experimental determination of the jacket pressure coefficient.

A Primary Dead-Weight Tester for Pressures (0.05-1.0) MPa.

Recent advances in technology on two fronts, 1) the fabrication of large-diameter pistons and cylinders with good geometry, and 2) the ability to measure the dimensions of these components with high accuracy, have allowed dead-weight testers at the National Institute of Standards and Technology (NIST) to generate pressures that approach total relative uncertainties previously obtained only by manometers. This paper describes a 35 mm diameter piston/cylinder assembly (known within NIST as PG-39) that serves as a pressure standard in which both the piston and the cylinder have been accurately dimensioned by Physikalisch Technische Bundesanstalt (PTB). Both artifacts (piston and cylinder) appeared to be round within ±30 nm and straight within ±100 nm over a substantial fraction of their heights. Based on the diameters at 20 °C provided by PTB (±15 nm) and on the good geometry of the artifact, the relative uncertainties for the effective area were estimated to be about 2.2 × 10−6 (1σ).

A Double-Primary Dead-Weight Tester for Pressures (35-175) kPa in Gage Mode.

Primary pressure standards in the atmospheric pressure range are often established using mercury manometers. Less frequently, controlled-clearance dead-weight testers in which one component (normally the piston) has been dimensionally measured have also been used. Recent advances in technology on two fronts i) the fabrication of large-diameter pistons and cylinders with good geometry; and ii) the ability to measure the dimensions of these components, have allowed some dead-weight testers at NIST to approach total relative uncertainties (k = 2) in dimensionally-derived effective areas near 5 × 10−6. This paper describes a single piston/cylinder assembly (NIST-PG201WC/WC) that serves as both a primary gage in which both piston and cylinder are measured dimensionally and a controlled-clearance primary gage (employing the Heydemann-Welch method). Thus it allows some previous assumptions about the modeling of dead-weight testers to be checked. For the gage described in this paper the piston/cylinder clearance obtained from the two analyses have relative differences of 4 × 10−6 to 7 × 10−6 over the pressure range 35 kPa to 175 kPa. Some implications of these results will be discussed. From the dimensional characterizations and auxiliary measurements we have determined that the effective area for this gauge at 20 °C is: Aeff,20=1961.0659mm2(1+3.75×10−12P/Pa+3.05×10−12PJ/Pa),where P is the system pressure and PJ is a control pressure. The estimated relative uncertainty in effective area is 8.2 × 10−6 +1.4 × 10−11 P/Pa (k = 2). The temperature coefficient for the area was measured and found to be (9.06 ± 0.04) × 10−6/K. Thus using the gage at a reference temperature of 23 °C yields an effective area: Aeff,23=1961.1192mm2(1+3.75×10−12P/Pa+3.05×10−12PJ/Pa),with almost no increase in the uncertainty over that at 20 °C.

A primary pressure standard at 100 kPa

Primary pressure standards in the atmospheric pressure range are often established using mercury manometers. To a lesser extent, controlled-clearance dead-weight testers, in which one component (normally the piston) has been dimensionally measured, have also been used. The recent advances in technology on two fronts: (i) the fabrication of large-diameter pistons and cylinders with good geometries; and (ii) the dimensional metrology capability of these components, have allowed some dead-weight testers at the National Institute of Standards and Technology (NIST) to achieve total relative uncertainties (2 σ) in generated pressure near 10 × 10-6 (10 ppm). This paper describes recent developments at the NIST in which accurate dimensional measurements have been translated into effective areas. It is anticipated that total relative uncertainties in generated pressure may decrease to 5 ppm (2 σ) when recent dimensional measurements are incorporated in the newest gauges.

Characterisation of a 1 GPa piston-cylinder unit

The accurate determination of distortion coefficients for dead-weight testers operating at high pressures has been treated by many authors using various methods, contributing to a better understanding of uncertainties in high pressure metrology. This paper addresses the characterisation of a dead-weight tester in a unique mathematical approach incorporating the elastic distortions and fluid properties of the transmitting fluid. The system comprises a high pressure assembly operating at 400 MPa. The study of the system behaviour extends beyond the nominal operating pressure range up to 1 GPa. The integrity of the models developed is based on theoretical and experimental validations carried out on other gas and oil operated balances. Results presented show a clear deviation from the formerly adopted “typical” behaviour of balance assemblies, including values used to correct for the uncertainty of pressure generated.

Primary pressure standard for calibration in the medium vacuum range

Primary standards for gas pressure in the range from ∼0.1 to 10 Pa (1 to 100 mTorr) have received a significant amount of attention in recent years. The interest in the calibration capability in this vacuum range is, to some degree, driven by the increasingly stringent requirements for the semiconductor processing industry. We present a new standard that is based on calculating the gas pressure required to restore a diaphragm to a null position, while the diaphragm is tilted to various, measured inclinations. With this as a basis, the calculations are relatively simple; there are no gas property dependent effects; and the system design is simple, robust, and easily automated. A formal evaluation of uncertainty for the system being developed in this facility is reviewed and compared with other primary standards. For the medium vacuum range, it is anticipated that this standard will offer numerous practical advantages relative to liquid manometers, dead weight testers, volume expansion systems, and conductance-based systems. It is intended that this technique will enable more widespread capability for the calibration, and verification of vacuum gauging in a pressure range of critical interest to many processes.

New High-precision Reference Pressure Transducers from 1 MPa to 50 MPa

Calibration laboratories prefer to use piston manometers (dead-weight testers) for calibrating pressures in the range from a few pascals up to 1 000 MPa. The high-precision pressure transducer P31AP is an alternative that can be calibrated as a secondary pressure standard and used as a reference pressure transducer. When using reference pressure transducers a simple manual or motor-driven pressure source should be available. The test pressure has no longer to be produced precisely as the actual pressure value can be measured by the reference pressure transducer at any time. Therefore there is nothing to prevent complete computer-controlled calibration of pressure transducers.

High pressure-high temperature laboratory apparatus for the measurement of deep sea sediment physical properties

Laboratory equipment has been built which will measure the permeability and thermal conductivity of deep-sea sediments at their in-situ conditions of hydrostatic pressure, temperature, and void ratio. The apparatus has the capability of uniaxially consolidating a sediment sample to simulate compaction within the sediment column, while exposing the specimen to hydrostatic pressures ranging from atmospheric to 62 MPa and to temperatures from 22 to 220°C. The equipment includes a hypodermic needle mounted vertically through the base of the pressure vessel from which thermal conductivity is determined by the needle probe method. The system also features a combination of dead-weight testers which produces a small hydraulic gradient across the sample and permits the measurement of sediment permeability at large hydrostatic pressures. The physical property data generated from this apparatus will be important in understanding the mechanisms of heat transfer through the ocean floor and in analysing the coupled flow of heat and pore fluid in the vicinity of a heat source, such as a radioactive waste canister, buried in the seabed.

Recent studies of float and stall curves in controlled-clearance deadweight testers with a simple piston

The effect of piston rotation speed and fluid viscosity on the performance of free-piston gauges with a controlled clearance was studied as part of an experimental program aiming at the better evaluation of pressure by these primary pressure standards. Calculated effective area is shown to be greatly influenced by both speed of rotation and choice of a fluid. An optimum rpm resulting in the smallest possible uncertainty in effective area should be determined experimentally for each fluid and pressure range involved. When all the pertinent parameters are properly selected an appreciable improvement in accuracy can be achieved.

Differential Pressure Transmitters, Span-Shift Errors With Static Pressure

The author reviews methods of calibrating low-differential (25–300 in. H2O) D.P. transmitters at high (up to 3000 psig) static pressure. Various test methods are described along with discussion of their merits. Included are use of one or more deadweight testers (gas or liquid) and use of a high-pressure mercury manometer as a standard. Five D.P. transmitters of different construction are tested and their static span-shift performance reported.